Co-reporter:Chao Dong, Xiang Li, Anjie Wang, Yongying Chen
Catalysis Today 2017 Volume 297(Volume 297) pp:
Publication Date(Web):15 November 2017
DOI:10.1016/j.cattod.2017.05.045
•The addition of Na+ and K+ to MCM-41 decreased the dispersion of Pd and Pt.•The electron densities of Pd and Pt increased with the addition of Na+ and K+.•Na+ and K+ inhibited the adsorption and dissociation of H2 on the catalysts.•Na+ and K+ showed a push-pull effect on the reaction performances of the catalysts.•Both Na+ and K+ did not affect the catalyst deactivation.Na+ and K+ were introduced to siliceous MCM-41 (Si-MCM-41) by ion-exchange of Si-MCM-41 with sodium oxalate or potassium oxalate, respectively. The supported Pd and Pt catalysts were prepared by an incipient wetness impregnation method. Their hydrodesulfurization (HDS) performances were evaluated using dibenzothiophene as the model molecule. The introduction of Na+ or K+ led to a decrease in the metal dispersions but an increase in the electron densities of metal sites. It also strongly inhibited the adsorption, dissociation, and probably the spillover of H2 on the catalysts. Independent of the type of metal, a push-pull effect of Na+ and K+ on the HDS performances of the Pd and Pt catalysts was observed. They on the one hand enhanced the direct desulfurization pathway (DDS), but on the other hand hindered the hydrogenation route. The DDS activity of Pt increased almost linearly with its electron density. These are discussed by considering both the negative effects of Na+ and K+ on the formation of active hydrogen species and their positive role on the electron densities of the metal sites. The Pt catalysts deactivated faster than the Pd catalysts. The kinetic study indicates that Na+ and K+ did not affect the deactivation of the catalysts.Download high-res image (148KB)Download full-size image
Co-reporter:Chao Dong, Xiang Li, Anjie Wang, Yongying Chen, Haiou Liu
Catalysis Communications 2017 Volume 100(Volume 100) pp:
Publication Date(Web):1 September 2017
DOI:10.1016/j.catcom.2017.07.003
•Pd nanoparticles were confined in the mesopores of a siliceous MCM-41 (Pd/MCM-41).•Pd nanoparticles were on the external surface of a silylated MCM-41 (Pd/S-MCM-41).•The electron density of Pd in Pd/S-MCM-41 was lower than that in Pd/MCM-41.•Pd/S-MCM-41 behaved much better than Pd/MCM-41 in selective hydrogenation reactions.•Pd/S-MCM-41 possessed a lower hydrogenolysis activity than Pd/MCM-41.Two different nanoscale Pd particle distributions in MCM-41, i.e. in the mesopores and on the external surface, were obtained by using a siliceous MCM-41 and a silylated MCM-41 (S-MCM-41) as the starting support materials, respectively. The electron density of Pd in Pd/S-MCM-41 was lower than that in Pd/MCM-41. Pd/S-MCM-41 exhibited much better selective hydrogenation performance but a lower hydrogenolysis activity than Pd/MCM-41. These differences are related to the different Pd particle distributions in MCM-41 and S-MCM-41, demonstrating that the performance of noble metal catalysts is tunable by simply controlling the nanoscale metal particle distribution in the pores.Download high-res image (152KB)Download full-size image
Co-reporter:Song Tian;Dr. Xiang Li;Dr. Anjie Wang;Dr. Roel Prins;Yongying Chen; Yongkang Hu
Angewandte Chemie International Edition 2016 Volume 55( Issue 12) pp:4030-4034
Publication Date(Web):
DOI:10.1002/anie.201510599
Abstract
Preparation of Ni2P by temperature-programmed reduction (TPR) of a phosphate precursor is challenging because the P−O bond is strong. An alternative approach to synthesizing Ni2P, by reduction of nickel hexathiodiphosphate (Ni2P2S6), is presented. Conversion of Ni2P2S6 into Ni2P occurs at 200–220 °C, a temperature much lower than that required by the conventional TPR method (typically 500 °C). A sulfur-containing layer with a thickness of about 4.7 nm, composed of tiny crystallites, was observed at the surface of the obtained Ni2P catalyst (Ni2P−S). This is a direct observation of the sulfur-containing layer of Ni2P, or the so-called nickel phosphosulfide phase. Both the hydrodesulfurization activity and the selective hydrogenation performance of Ni2P-S were superior to that of the catalyst prepared by the TPR method, suggesting a positive role of sulfur on the surface of Ni2P-S. These features render Ni2P-S a legitimate alternative non-precious metal catalyst for hydrogenation reactions.
Co-reporter:Song Tian;Dr. Xiang Li;Dr. Anjie Wang;Dr. Roel Prins;Yongying Chen; Yongkang Hu
Angewandte Chemie 2016 Volume 128( Issue 12) pp:4098-4102
Publication Date(Web):
DOI:10.1002/ange.201510599
Abstract
Preparation of Ni2P by temperature-programmed reduction (TPR) of a phosphate precursor is challenging because the P−O bond is strong. An alternative approach to synthesizing Ni2P, by reduction of nickel hexathiodiphosphate (Ni2P2S6), is presented. Conversion of Ni2P2S6 into Ni2P occurs at 200–220 °C, a temperature much lower than that required by the conventional TPR method (typically 500 °C). A sulfur-containing layer with a thickness of about 4.7 nm, composed of tiny crystallites, was observed at the surface of the obtained Ni2P catalyst (Ni2P−S). This is a direct observation of the sulfur-containing layer of Ni2P, or the so-called nickel phosphosulfide phase. Both the hydrodesulfurization activity and the selective hydrogenation performance of Ni2P-S were superior to that of the catalyst prepared by the TPR method, suggesting a positive role of sulfur on the surface of Ni2P-S. These features render Ni2P-S a legitimate alternative non-precious metal catalyst for hydrogenation reactions.
Co-reporter:Jin Bai, Xiang Li, Anjie Wang, Roel Prins, Yao Wang
Journal of Catalysis (March 2012) Volume 287() pp:161-169
Publication Date(Web):1 March 2012
DOI:10.1016/j.jcat.2011.12.018
The hydrodesulfurization (HDS) of dibenzothiophene (DBT) and its hydrogenated intermediates 1,2,3,4-tetrahydro-dibenzothiophene (TH-DBT) and 1,2,3,4,4a,9b-hexahydro-dibenzothiophene (HH-DBT) over a bulk MoP catalyst was studied at 340 °C and 4 MPa both in the presence and absence of piperidine. The results indicated that sulfur was incorporated on the surface of MoP during HDS reactions, probably leading to the formation of new active sites, which possessed higher direct desulfurization (DDS) activity than the fresh MoP. The hydrogenation pathway and DDS pathway played an equally important role in the HDS of DBT. The desulfurization of TH-DBT was much faster than that of DBT, whereas HH-DBT mainly desulfurized by dehydrogenation to TH-DBT and subsequent desulfurization of TH-DBT. Piperidine decreased the rates of all reactions, but that of hydrogenation more than of desulfurization. It not only competed with the sulfur-containing molecules for adsorption on the active sites but also slowed down the sulfidation of MoP surface.Graphical abstractDownload high-res image (121KB)Download full-size imageHighlights► Sulfur was incorporated on the surface of MoP in HDS reactions. ► The sulfided MoP possessed higher direct desulfurization activity than fresh MoP. ► Piperidine slowed down the sulfidation of MoP. ► Reaction network and rate constants for all steps in the HDS of DBT over MoP.
Co-reporter:Lei Yang, Xiang Li, Anjie Wang, Roel Prins, Yao Wang, Yongying Chen, Xinping Duan
Journal of Catalysis (August 2014) Volume 317() pp:144-152
Publication Date(Web):1 August 2014
DOI:10.1016/j.jcat.2014.06.020
•Kinetics of the HDS of 4,6-dimethyldibenzothiophene over Ni2P.•A fast dehydrogenation of tetrahydro-4,6-dimethyldibenzothiophene (TH-4,6-DMDBT).•Methyl group migration during the dehydrogenation of TH-4,6-DMDBT.•Inhibition of desulfurization by piperidine depends on reactant.The hydrodesulfurization (HDS) of 4,6-dimethyldibenzothiophene (4,6-DMDBT) and its hydrogenated intermediates 1,2,3,4-tetrahydro-4,6-dimethyldibenzothiophene (TH-4,6-DMDBT) and 1,2,3,4,4a,9b-hexahydro-4,6-dimethyldibenzothiophene (HH-4,6-DMDBT) over a bulk Ni2P catalyst was studied at 340 °C and 4.0 MPa in the presence and absence of piperidine. The rate constants of all steps in the network of the HDS of 4,6-DMDBT were measured. The HDS of 4,6-DMDBT occurred predominantly through the hydrogenation (HYD) pathway, and the HYD and direct desulfurization pathways were about equally inhibited by piperidine. Piperidine inhibited the desulfurization of TH-4,6-DMDBT and 4,6-DMDBT in the same way, but did not affect that of HH-4,6-DMDBT. In contrast to the HDS of TH-4,6-DMDBT over metal sulfide catalysts and to the HDS of TH-DBT, a fast dehydrogenation of TH-4,6-DMDBT to 4,6-DMDBT was observed. Besides 4,6-DMDBT, a small amount of the methyl-migration isomers was detected in the dehydrogenation product of TH-4,6-DMDBT, which is ascribed to the metallic character of Ni2P.Graphical abstractDownload high-res image (212KB)Download full-size image
Co-reporter:Jin Bai, Xiang Li, Anjie Wang, Roel Prins, Yao Wang
Journal of Catalysis (April 2013) Volume 300() pp:197-200
Publication Date(Web):1 April 2013
DOI:10.1016/j.jcat.2013.01.015
The surface of MoP becomes sulfided during hydrodesulfurization (HDS) of dibenzothiophene (DBT), and the HDS activity increases with time on stream, showing that the sulfided MoP surface is more active than the fresh MoP surface. MoP pretreated with H2S/H2 under HDS reaction conditions showed the same activity increase as fresh MoP, but XPS did not show any sulfur at the surface of the pretreated MoP. Hence, the sulfur that is incorporated into the MoP surface during the HDS of DBT originates from DBT rather than from H2S.Graphical abstractMoP pretreated with H2S/H2 under HDS reaction conditions showed the same activity increase as fresh MoP, suggesting that the sulfur incorporated into the MoP surface during the HDS of DBT originates from DBT rather than from H2S.Download high-res image (84KB)Download full-size imageHighlights► The HDS activity and BP selectivity of MoP increased with time on stream. ► The HDS performance of MoP was not affected by H2S pretreatment. ► No sulfur was detected at the surface of the H2S-pretreated MoP. ► The sulfur incorporated into the MoP surface during HDS originates from DBT rather than from H2S.
